Dissolving 33 g of salt in 120 g of water, a solution was obtained with a mass fraction of salt of 20%.

Dissolving 33 g of salt in 120 g of water, a solution was obtained with a mass fraction of salt of 20%. Calculate the mass of insoluble impurities contained in 33 g of salt.

1) Find the total mass of the resulting solution by the formula:

mass of solution = mass of substance + mass of solvent = 33 + 120 = 153 (g).

2) Since the impurities in the salt were insoluble, they did not affect the resulting concentration of the solution. Let’s calculate how much salt actually dissolved, forming a solution of 20% – concentration. To do this, you need the formula:

solute mass = solution percentage: 100% * solution mass.

Let’s substitute the data into it:

mass of salt without impurities = 20: 100% * 153 = 30.6 (g).

3) Calculate the mass of impurities:

impurity mass = 33 – 30.6 = 2.4 (g).